Corrugated Microfiber Webs
Corrugated and pleated webs of polymeric microfiber are known in the art and have been disclosed in the following U.S. Pat. Nos.: 5,038,775, 4,939,016, 4,910,064, 4,842,739, 4,826,642, 4,774,001, 4,759,782, 4,676,807, and 4,617,124.
U.S. Pat. No. 5,038,775 discloses a filter assembly that includes a pleated microfibrous web as a filter medium. The filter medium is maintained in a pleated condition by a scrim that extends over the upstream and downstream sides of the pleated filter medium to provide substantially continuous support to the filter medium.
U.S. Pat. No. 4,939,016 discloses a composite web material that includes a hydraulically entangled laminate of melt blown microfibers and a further layer, preferably at least one of pulp fibers, staple fibers, melt blown fibers, and continuous filaments, with or without particulate material. The patent discloses that this composite web can be formed into a corrugated stretchable fabric by pre-stretching the web and hydraulically entangling the web while stretched.
U.S. Pat. No. 4,910,064 discloses a nonwoven web that has a multiplicity of substantially longitudinally molecularly oriented continuous filaments of a thermoplastic polymer. Onto the longitudinal continuous filaments are deposited a multiplicity of melt blown fibers having fiber diameters of 0.5 to 50 micrometers (.mu.m). The melt blown fibers form bonds at some of their intersections with the longitudinal continuous filaments to stabilize and fix the orientation of those filaments. The stabilized continuous filaments are pleated or corrugated and are stabilized in that condition by depositing a layer of melt blown fibers on one side of the pleats or corrugations (column 26, lines 12-16).
U.S. Pat. No. 4,842,739 discloses a high surface area filter cartridge that contains a nested arrangement of disk-shaped filter layers. The disk-shaped filter layers have a pattern of regular radial pleats and comprise a laminate that includes an upstream prefilter layer, a filtration media, and a downstream cover layer. The filtration media can be a nonwoven web of melt blown microfibers. The filter laminate is pleated by an embossing operation.
U.S. Pat. Nos. 4,826,642 and 4,774,001 disclose a composite structure that is usefull as a flat filtration medium or as a pleated (corrugated) filtration structure. The composite structure comprises a microporous membrane and a synthetic thermoplastic web of microfibers secured to the microporous membrane by melt blowing the microfibers thereon
U.S. Pat. Nos. 4,759,782 and 4,676,807 disclose a cylindrical filter structure that may comprise a single pleated filter medium supported by an outer perforated, cylindrical support cage. The filter media may comprise organic melt blown microfibers. In Example 1, a composite, cylindrical pleated filter structure was prepared from two layers of melt-blown polyester fibrous material having two glass fiber layers sandwiched therebetween. The melt-blown polyester fibrous material contained fibers having diameters ranging from 35 to 50 .mu.m, and was calendared to a thickness of 0.009 inches (pore size was 100 .mu.m) before being combined with the glass fiber medium. The composite structure was placed in pleated form in a perforated polypropylene cage. No disclosure is provided as to how the composite structure is pleated.
U.S. Pat. No. 4,617,124 discloses a polymeric, microfibrous filter sheet where the microfiber is coated with a cured thermosetting binding resin or polymer. In column 24, lines 29-31, it is disclosed that the filter sheet can be placed in pleated form and incorporated into a cartridge.